Current limiting device

ABSTRACT

A current limiting fuse holder and method of making the same in which the metal fittings at each end of the fuse holder are secured to the glass resin impregnated filament wound tube or housing of the fuse holder by internal teeth. The fittings may be of the split type so that each half of the fitting may be compressed into the filaments before the latter are cured and have tapered teeth on the inside of a construction so that the teeth closest to the outer end are the longest and then decrease in length toward the inner end of the fitting so that the teeth penetrate and lock into different layers of the winding forming the housing. Under another embodiment, grooves may be machined into a cured filament wound tube and an annular fitting of different length teeth are threaded into the grooves. In both these cases, the fittings and the inner layers of the filaments of the tube or housing are overwound with glass resin impregnated filaments to lock the fittings in place and complete the housing and fuse tube after which the entire assembly is cured. In another embodiment of the invention, the split fitting is not overwrapped with the filaments but rather the fitting is externally threaded to receive a sleeve which is threaded onto the fitting after curing of the assembly or the fitting may be otherwise clamped to support the fitting in service.

United States Patent 1191 Harmon CURRENT LIMITING DEVICE [75] Inventor: Emerson R. Harmon, l-lartland, Wis.

[73] Assignee: The Amalga Corporation,

Menomonee Falls, Wis.

[22] Filed: July 9, 1973 [21] Appl. No.: 377,426

[52] US. Cl 337/246, 337/186, 337/227, 337/248 [51] Int. Cl. H0lh 85/36 [58] Field of Search 337/186, 205, 227, 228, 337/234, 246, 248, 251

[56] References Cited UNITED STATES PATENTS 2,289,207 7/1942 Papp 337/248 x 2,333,354 11/1943 Andersen et al 337/248 X 2,727,961 12/1955 Smith 337/246 X 3,156,801 11/1964 Cole et a1. 337/248 X Primary Examiner-J. D. Miller Assistant ExaminerFred E. Bell Attorney, Agent, or Firm-Andrus, Sceales, Starke & Sawall [57] ABSTRACT A current limiting fuse holder and method of making [11] 3,846,727 1 Nov. 5, 1974 the same in which the metal fittings at each end of the fuse holder are secured to the glass resin impregnated filament wound tube or housing of the fuse. holder by internal teeth. The fittings may be of the split type so that each half of the fitting may be compressed into the filaments before the latter are cured and have tapered teeth on the inside of a construction so that the teeth closest to the outer end are the longest and then decrease in length toward the inner'end of the fitting so that the teeth penetrate and lock into different layers of the winding forming the housing. Under another embodiment, grooves may be machined into a cured filament wound tube and an annular fitting of different length teeth are threaded into the grooves. in both these cases, the fittings and the inner layers of the filaments of the tube or housing are overwound with glass resin impregnated filaments to lock the fittings in place and complete the housing and fuse tube after which the entire assembly is cured. in another embodiment of the invention, the split fitting is not overwrapped with the filaments but rather the fitting is externally threaded to receive a sleeve which is threaded onto the fitting after curing of the assembly or the fitting may be otherwise clamped to support the fitting in service.

7 Claims, 13 Drawing Figures BACKGROUND OF THE INVENTION failure as compared to present devices which are not capable of withstanding the voltage levels obtained by the present invention.

SUMMARY OF THE INVENTION The invention is directed to a current limiting device and method of making the same for use in holding a fuse which, in service, may be subjected to surges of high voltages.

The fuse holder of the invention consists of a housing formed by layers of continuously wound glass fibers impregnated with a thermosetting resin. At each end of the housing there is located a metal fitting either of the split-ring type or of solid ring-type construction. Each fitting has internal tapered teeth and the teeth are of varying length. a

The longest tooth is located at the outer end of each fitting and the teeth gradually decrease in length so that the shortest tooth is located at the inner end of each fitting. The teeth of the fitting thus penetrate into different layers of the. winding of the housing and this effects transfer of the applied tensile load the metal fittings will be subjected to in service uniformly throughout the wall of the housing or fuse holder-tube. The fittings are overwound with layers of resin impregnated glass filaments to lock the fittings securely to the housing, andthe entire unit is cured.

Under one method of the invention, the resin impregnatedcontinuous glass fibers are wound back and forth about a mandrel to provide a housing or tube of a plurality of layers of filaments. The winding is then interrupted and split ring fittings are applied. over the uncured housing. The fittings internally have tapered teeth and the teeth are of different length, the longest tooth. being on the outer end of the fitting and the teeth gradually decrease in length to the shortest at the inner end of the fitting. The split ring fittings are compressedtogether into the uncured housing. The housing and fitting are returned to the winding machine and thefittings are overwrappedwith resin impregnated glass filaments to lock the fittings to the housing. Thereafter the fuse holder is finally cured and removed from the mandrel.

Under another embodiment of the invention after the ,housing is initially formed, it is cured on the mandrel and then removed and grooves of helical form and. of inwardly decreasing depth are machined in the ends of the housing. Metal solid ring-like fittings having tapered teeth or threads of different depth corresponding to the grooves are threaded into the grooves at the ends of the housing. Thereafter the fuse holder is placed on a. mandrel and the fittings are overwrappedwith thermosetting resin impregnated glass filaments and the windings are cured: and the completed fuse holder or current limiting device is removed from the mandrel.

Under another embodiment of the invention, the split fittings are not overwound with the resin impregnated filaments but instead the fittings are externally threaded and a sleeve is threaded onto each fitting to support the fitting in service.

Under all the described embodiments the tube or housing is formed on a mandrel of a considerable length sothat a plurality of fuse holders can be severed from a single elongated tube.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. l is a longitudinal section with parts in elevation illustrating a plurality of layers of filaments wound on a mandrel to provide the housing of the fuse holder;

FIG. 2 is a longitudinal section of the fuse holder of the invention with parts in elevational and without any fuse'in place but with the terminal fittings applied and overwrapped;

FIG. 3 is an enlarged longitudin alsection of afitting end of a fuse holder illustratingthe difference in the depth or length of the teeth of the terminal fitting and their penetration of the filament layers and the overwrapping thereof;

FIG. 4 is a cross section taken on line 44 of FIG. 3 to illustrate the split ring construction of the fitting;

FIG. 5 is a sectional view with parts in elevation illustrating the compressing of the split ring terminal fittings into the end of a fuse holder housing;

FIG. 6 is perspective view illustrating a second embodiment of the invention with grooves machined in the housing;

FIG. 7 is a detailed sectional view illustrating a solid ring-like terminal fitting threaded into the grooves;

FIG. 8 illustrates in elevation a locking ring secured around the fitting to hold it in place.

FIG. 9 is a top plan view of the locking ring before assembly with the fitting of FIG. 8;

FIG. 10 is a side elevational view of a fuse holder with parts in section illustrating another embodiment of the invention.

1-7 having an elongated housing I provided by a plu- FIG. 11 is a side elevational view with parts in section and illustrating a split ring terminal fitting threaded throughout, and which has been assembled on the resin impregnated filament wound tube;

FIG. 12 is a side elevation with parts in section illustrating the holding of the split fitting on the tube during curing; and

FIG. 13 is a side elevation with parts in section of the tube and split ring fitting with a locking sleeve threaded onto the fitting to support the fitting in .service.

Referring to the drawings, there is shown a fuse holder or current limiting device as illustrated in FIGS.

rality of layers of continuous glass fibers impregnated with a thermosetting resin applied by the filament winding method. Layers 2, 3, 4 and 5 of the fibers are illustrated in FIG. 3.

The metal terminal fittings 6 are located on the ends of housing 1 and only one fitting will be described as both are the same. The fitting 6 is of the split ring type as illustrated in FIG. 4 and has threads 7 at the outer end for receiving a terminal plug, not shown, and which approach a flange or abutment 8 extending around the body of each half ring of fitting 6.

Internally fitting 6 is provided with the longitudinally spaced and tapered relatively sharp teeth 9. The teeth 9 are shown as equidistant from each other and the outermost tooth 9 is the longest, and the teeth 9 inwardly of outermost tooth 9 decrease in length to the shortest tooth 9 which is the innermost tooth.

The split ring fitting 6 is assembled with layers 2, 3, 4 and 5 of housing 1 when they are uncured by compressing the two halves of the fitting as shown in FIG. 5 into the uncured filament winding layers 2, 3, 4 and 5. Therefore, as illustrated in FIG. 3, the outermost tooth 9 will penetrate into innermost filament layer 2. The next adjacent tooth will penetrate into layer 3 and the next into layer 4, and the innermost tooth 9 will penetrate into outermost filament layer 5. The teeth 9 slant slightly outwardly and preferably extend annularly around each half of the fitting and may be at a slight helix but are not necessarily continuously connected throughout the internal extent of the fitting. By locking the teeth into separate layers of filaments, the

effect is to transfer the tensile load on the metal end fittings, which is applied upon fuse interruption, uniformly throughout the wall of housing 1.

In carrying out the method of the invention with respect to the embodiment illustrated in FIGS. 1-4 of the drawing, the first step consists of winding continuous glass fibers impregnated with a thermosetting resin about-the mandrel 11 to provide a plurality of layers of filaments such as layers 2, 3, 4 and 5. This is accomplished by rotating the winding mandre 11 having a diameter corresponding to the inside'diameter of the completed fuse holder in a machine, not

shown, capable of dispensing glass roving or fibers impregnated with a thermosetting resin along a predetermined path and under controlled tension. The illus- I trated layers 2, 3, 4 and 5 are wound at a low angle with respect to the center line of mandrel l1 which'will yield maximum tensile values. The housing 1 formed by layers 2-5 is ordinarily made of considerable length so that itcan then later be severed'into the length desire for each respective fuse holder.

Thewinding process is then interrupted and before any curing operation, the mandrel l1 and the incompleted housing or tube is removed from the machine and assembled in supporting fixtures 12 so that one portion ofthe assembled unit rests on the top of half of 'a split-ring fitting, as shown on the right side of the drawingof FIG. 5 which is held by fixtures l2, and another part of the unitrests on additional, split rings held bythe other fixture 12. Referring only to the fitting assembly shown at the right of FIG. 5, the other half of split ring fitting 6 is then placed over the housing 1 in line with the first half of fitting 6 and the piston 13 of the fixture is lowered by power cylinder 14 to force the internal teeth 9 of the fitting 6-to penetrate the filament layers2, 3,4 and 5. The fitting 6 at the left hand side of FIG. 5 is similarly assembled. FIG. 5 shows housing 1 and the mandrel 11' cut off to illustrate the elongation of housing land the severing thereof to provide a number of fuse tubes.

Thereafter, the mandrel 11 with the winding layers 2,

I invention in which a solid annular fitting 15 having in- 4 to lock thevfittings 6 into place and to build up layers of fibers to the desired wall thickness. The completed housing 1 is then cured, the mandrel 11 is extracted, and the low angle winding cut off flush with the fitting ends. 4

FIGS. 6 and 7 illustrate another embodiment of the ternal teeth vl6 corresponding to those of fitting 6 in that the outermost tooth 16 is the longest and the teeth gradually decrease in length to the innermost shortest tooth 16. In this embodiment theteeth 16 may be on a slight helix or annular but preferably extend continuously on a helix internally of the fitting.

In this embodiment, the layers of resin impregnated glass filaments wound on the mandrel 11 are cured and the mandrel 11 is extracted therefrom. The grooves 17 are then machined into the ends of fuse holders of a depth corresponding to the varying length of the teeth 16 of fittinglS. Fitting 15 is then threaded onto the end 1 of the cured layers as shown in FIG. 7 to locate the teeth 16 in grooves 17 at varying depths to penetrate under the method of the second embodiment of the in- 3, 4 and 5 thereon and fittings 6 secured thereto is re- 6 turned to the winding machine, not shown, and a plurality of layers 10 of continuous glass fiber impregnated with a thermosetting resin are wrapped over layers 2, 3, 4 and 5 at a high angle with respect to the centerline of mandrel l1 and back and forth over metal fittings 6 30 which extends annul'arly therearound slightly revention.

FIG. 8 illustrates another embodiment of the invention for mechanically holding the fitting during curing.

In this embodiment, the split ring fitting 18 there shown as in the first embodiment has teeth 19 which are embedded in the filament wound tube'20 but is provided with'horizontally spaced flanges 21. The compressing of theteeth 19 into tube 20 is done when the filaments are in the uncured state such as by the fixture l2, piston l3 and power cylinder 14 illustrated in FIG. 5. However, simultaneously the fixture and piston wrap a locking ring 22 around fitting 18, not shown, between flanges 21 to secure fitting 18 in place. As illustrated locking ring 22 has a tab 23 at one end which in the locking operation is received within the key slot 24 at FIG. 10 illustrates another embodiment of a completed fuse tube assembly which has an inner fuse liner 25 around which is located a layer of hoop windings 26.

The hoop windings 26 are encircled by a layer of low angle windings 27. In both cases there are several layers of both types of windings but only one layer of each is illustrated. The split terminal fitting 28 is'shown as assembled in place and has the teeth: 29 of different lengths which extend into different layers of the windings with the longest tooth being the outermost of the teeth 29 and the shortest tooth 29 being the innermost tooth. The split terminal fitting 28 also has the groove moved from the outer end of fitting 28. An annular end sleeve 31 which in construction is flared outwardly and has an internal flange 32 which is disposed over the end of fitting 28 and sleeve 3l is compressed in assembly to force or crimp flange 32 into groove 30 of fitting 28. The sleeve 31 is threaded internally to receive the desired connection and supports the split fitting 28 in service. As shown a sleeve 31 is also located over the split fitting, not shown, at the other end of the fuse holder, and a molded plastic sleeve 33 is assembled and secured over the body of the .fuse holder.

In assemblying the fuse tube of FIG. 10, the tube is initially formed on the mandrel 11 by windings 26 and 27. The split fitting 28 is then assembled over the tube and held in place by C-clamp 38 or the like and cured. Thereafter the mandrel 11 is extracted and the tube is cut to length. After the cutting operation the plastic sleeve 33 is assembled over the tube, and the flared end fittings or end sleeve 31 is compressed into place on each end of the fuse tube to support the split fitting 28.

FIG. 11 illustrates a split terminal fitting 34 which has the teeth 35 of different length which penetrate different layers of the filaments in tube 35 and slant slightly outwardly. The filament layers consist of a plurality of internal hoop layers 36 and around which are wound a plurality of layers 37 of filaments at a low angle helix. The fitting 34, however is threaded externally generally throughout its length and as in the first embodiment, the fitting 34 is assembled with the uncured windings of tube 35 by compressing the two halves of the fitting 34 as shown in FIG. 5 so that the teeth 35 penetrate different layers of the uncured windings the same as is illustrated in the previously described embodiments of the invention. The fitting 34 is then clamped in the compressed position such as by C-clamp 38 shown in FIG. 12, and the completed tube and fitting assembly is then cured. The mandrel upon which the tube has v been assembled is thereafter extracted and the assembly is cut from the elongated tube 35 50 form fuse holder of the proper length as illustrated in the completed fuse holder shown in FIG. 13.

The fuse holder is then completed by threading the annular sleeves 39 onto the split fittings 34 at each end of the fuse holder. The sleeves 39 hold and support fitting 34 in place in service. By employing sleeves 39 as illustrated in this embodiment, this eliminates a second winding operation to secure the fitting in place.

In the method of the last described embodiment the inner hoop layers of the resin impregnated filament wound tube are first formed bywinding the filaments on a mandrel such as mandrel 11 shown in FIG. 1.

Thereafter, over the hoop layers are wound resin impregnated filaments at a low angle helix. The uncured tube and each split ring terminal fitting 34 with the mandrel is then assembled within a fixture such as that illustrated in FIG. 5 and the teeth ofthe fitting are compressed into different layers of the filament-windings.

The assembly is removed and clamped with C-clamps 38 and cured Thereafter the mandrel is removed and selected lengths of the tube are severed to form the desired length of each fuse holder. Then the C-clamps 38 are removed and a sleeve 39 is threaded home on each fitting 34 to support the fitting in service.

The fuse holder of the invention and the method of making the same provides a fuse holder in which the I claim: 7

l. A current limiting fuse holder, which comprises a tubular housing formed of layers of filament wound fibers impregnated with a thermosetting resin, at least one terminal fitting having internal teeth secured to an end of the housing by the teeth being embedded within different layers of filament wound fibers, and means overlaying the terminal fitting to lock the fitting in place.

2. The current limiting fuse holder of claim 1 in which the terminal fitting is a split ring.

3. The current limiting fuse holder of claim 2, in which the split ring has tapered teeth in that the teeth extending from the outer end of the fitting to the inner end are longestat the outer end and gradually decrease in length to the inner end to engage different layers of the filament windings and are slanted outwardly of the tubular housing.

4. The current limiting fuse holder of claim 1 in which the terminal fitting is of annular solid ring-like construction with internal teeth of varying length, and matching grooves provided in the end of the housing to permit threading of the fitting into the grooves.

5. The current limiting fuse holder of claim 1 in which the means overlaying the terminal fitting are resin impregnated filament windings wound over the terminal fitting.

6. The current limiting fuse holder of claim 1 in which the means overlaying the terminal fitting is a sleeve threaded onto the fitting.

7. The current limiting fuse holder of claim 1 in which the terminal fitting has an external annular groove spaced from the outer end of the fitting, and the means overlaying the fitting is an end sleeve having an annular flange disposed in the groove of the fitting to hold the fitting in place in service. 

1. A current limiting fuse holder, which comprises a tubular housing formed of layers of filament wound fibers impregnated with a thermosetting resin, at least one terminal fitting having internal teeth secured to an end of the housing by the teeth being embedded within different layers of filament wound fibers, and means overlaying the terminal fitting to lock the fitting in place.
 2. The current limiting fuse holder of claim 1 in which the terminal fitting is a split ring.
 3. The current limiting fuse holder of claim 2, in which the split ring has tapered teeth in that the teeth extending from the outer end of the fitting to the inner end are longest at the outer end and gradually decrease in length to the inner end to engage different layers of the filament windings and are slanted outwardly of the tubular housing.
 4. The current limiting fuse holder of claim 1 in which the terminal fitting is of annular solid ring-like construction with internal teeth of varying length, and matching grooves provided in the end of the housing to permit threading of the fitting into the grooves.
 5. The current limiting fuse holder of claim 1 in which the means overlaying the terminal fitting are resin impregnated filament windings wound over the terminal fitting.
 6. The current limiting fuse holder of claim 1 in which the means overlaying the terminal fitting is a sleeve threaded onto the fitting.
 7. The current limiting fuse holder of claim 1 in which the terminal fitting has an external annular groove spaced from the outer end of the fitting, and the means overlaying the fitting is an end sleeve having an annular flange disposed in the groove of the fitting to hold the fitting in place in service. 